Method of manufacturing electronic component and electronic component

ABSTRACT

A method of manufacturing an electronic component capable of preventing entrance of a plating solution and a flux component at an interface to which an inner electrode of a ceramic element body is extended, and capable of forming an outer electrode of an arbitrary shape. A ceramic element body is made of a ceramic material containing a metal oxide, and part of an inner electrode is extended to extended surfaces of the ceramic element body. A base electrode is formed on each of the extended surfaces using a conductive paste to be connected to the inner electrode. Part of another surface of the ceramic element body adjacent to the extended surfaces is locally heated, and part of the metal oxide is reduced to form a reformed portion. A plating electrode is continuously formed over the base electrode and the reformed portion through a plating method to form outer electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.16/374,649, filed Apr. 3, 2019, which claims benefit of priority toInternational Patent Application No. PCT/JP2017/043633, filed Dec. 5,2017, and to Japanese Patent Application No. 2016-241005, filed Dec. 13,2016, the entire contents of each are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to a method of manufacturing anelectronic component, and a method of manufacturing an electroniccomponent, particularly relating to forming an outer electrode on aceramic element body.

Background Art

In an existing method of forming an outer electrode of an electroniccomponent, in general, an electrode paste is applied to each end surfaceof a ceramic element body. The electrode paste is subsequently baked orcured to form a base electrode, and then, a plating electrode is formedon the base electrode by a plating process.

For application of the electrode paste, a method of dipping an endportion of the electronic component into a paste film formed with apredetermined thickness or a method of using a transfer by a roller orthe like is used. In these techniques, there is a problem that anodd-shaped outer electrode, including an L-shaped electrode, cannot beformed or is difficult to be formed.

In addition, in place of the electrode forming method using theelectrode paste as described above, a method has been proposed in whicha plurality of end portions of inner electrodes is exposed close to eachother on an end surface of a ceramic element body, dummy terminalscalled an anchor tab are exposed close to the end portions of the innerelectrodes on the same end surface, and electroless plating is performedon the ceramic element body, whereby a plating metal is grown using theend portions of the inner electrodes and the anchor tabs as cores, andan outer electrode is formed as described, for example, in JapaneseUnexamined Patent Application Publication No. 2004-40084. With thismethod, the odd-shaped outer electrode can be relatively easily formed.

However, in this method, since the outer electrode is formed by directdeposition of the plating on the end portion of the inner electrode andthe anchor tab, there is a possibility that a plating solution entersand remains in a boundary between the ceramic element body and the endportion of the inner electrode, or a boundary between the ceramicelement body and the anchor tab. In addition, there is also apossibility that flux contained in solder enters and remains in aninterface portion between the ceramic element body and the innerelectrode at the time of mounting. These plating solution and fluxremaining in the ceramic element body may cause defects such ascorrosion or the like under a use environment.

FIGS. 13A through 13C illustrate a cross section of an example of a chipcomponent in a case where an outer electrode is formed only by a platingmethod as disclosed in Japanese Unexamined Patent ApplicationPublication No. 2004-40084. A reference numeral 100 denotes a ceramicelement body, a reference numeral 101 denotes an inner electrode, and areference numeral 102 denotes an extended portion of the innerelectrode. When the ceramic element body 100 is fired, a gap 103 may begenerated between the extended portion 102 and the ceramic element body100 at an interface portion where the inner electrode 101 is extended asillustrated in FIG. 13B due to a difference in shrinkage between theceramic element body 100 and the inner electrode 101. When plating isperformed in this state, a plating solution enters the gap 103 asillustrated in FIG. 13C, and the plating solution is sealed by a platingelectrode 104.

SUMMARY

The present disclosure provides a method of manufacturing an electroniccomponent and an electronic component, capable of preventing entrance ofa plating solution or a flux component at an interface to which an innerelectrode of a ceramic element body is extended, and capable of formingan outer electrode of an arbitrary shape.

According to the present disclosure, an electronic component with anouter electrode formed on a ceramic element body through the followingsteps is manufactured. First, as illustrated in a step (A) of FIG. 12 ,a ceramic element body made of a sintered ceramic material containing ametal oxide is prepared. Here, the ceramic element body has an innerelectrode, and part of the inner electrode is extended to an extendedsurface. Next, as a step (B), a base electrode is formed on the extendedsurface of the ceramic element body so as to be connected to the innerelectrode. This base electrode is formed through an electrode formingmethod using a conductive paste or a dry plating method. Next, as a step(C), by locally heating part of another surface of the ceramic elementbody adjacent to the extended surface and by reducing part of the metaloxide, a reformed portion is formed. Next, as a step (D), a platingelectrode is formed on the base electrode and the reformed portionthrough a wet plating method, and as a result, an outer electrode isformed.

The present disclosure proposes a method of forming the outer electrodeby combining a plurality of kinds of techniques. In other words, first,the base electrode is formed on the extended surface of the innerelectrode of the ceramic element body using a method other than the wetplating method. Specifically, the base electrode is formed by theelectrode forming method using the conductive paste or the dry platingmethod. With this, the base electrode and an extended portion of theinner electrode are electrically connected to each other. Since noplating solution is used at the time of forming the base electrode, evenif there is a gap at an interface to which the inner electrode of theceramic element body is extended, the gap is closed by the baseelectrode. Note that the base electrode does not need to be formed onlyon the extended surface, and may be extended to part of another surfaceadjacent to the extended surface. The base electrode does not need to beformed on the entire surface of the extended surface, and it issufficient for the base electrode to be formed at least on a portionwhere the inner electrode is extended.

Next, by locally heating part of another surface of the ceramic elementbody adjacent to the extended surface and by reducing part of the metaloxide included in the ceramic element body, the reformed portion isformed. This reformed portion is a portion having a lower resistancevalue than that of the other portion of the ceramic element body. Notethat either step may be performed first in a formation order of the baseelectrode and the reformed portion.

After forming the base electrode and the reformed portion, the platingelectrode is formed on the base electrode and the reformed portionthrough the wet plating method. The reformed portion is a portion whoseresistance value is lower than that of a non-reformed portion of theceramic element body, and can therefore serve as a deposition startingpoint of a plating metal. Since the base electrode is of courseelectrically conductive, it is possible to easily deposit the platingmetal. Even if the gap is generated at the interface to which the innerelectrode of the ceramic element body is extended, since the gap isalready closed by the base electrode, it is possible to prevent theplating solution from entering the gap during the plating process. Bythe plating process, the plating electrode is formed on the baseelectrode and the reformed portion, and as a result, the outer electrodeis formed. Note that even if the base electrode and the reformed portionare slightly separated from each other, the plating metal rapidly growsusing the plating metal deposited on both elements as a core, so that acontinuous plating electrode can be formed. Note that in the case wherethe base electrode and the reformed portion are formed so as to beseparated from each other, the plating electrode may be independentlyformed on each of them. The formation of the plating electrode may beperformed a plurality of times. In other words, the plating electrodemay have a multilayer structure. As is well known, the wet platingmethod is advantageous in that it is possible to form a uniformelectrode with excellent mass productivity at a low cost.

A method of forming the base electrode using the conductive pasteincludes a method of forming the base electrode by applying a conductivepaste containing glass and metal powder on the extended surface of theceramic element body and sintering the metal powder by heat treatment, amethod of forming the base electrode by applying a conductive pastecontaining a thermosetting resin and metal powder on the extendedsurface of the ceramic element body and curing the thermosetting resinby heat treatment, and the like. In the latter method, the baseelectrode can be formed at a relatively low temperature compared withthe former method. In the present specification, the conductive pasteand the electrode paste are used interchangeably. As the dry platingmethod, for example, a vapor deposition method, a sputtering method, orthe like may be used. Any of the methods is an electrode forming methodthat does not use the plating solution, and it is possible to preventthe plating solution from entering the gap generated at the interfacebetween the ceramic element body and the extended portion of the innerelectrode.

As a local heating method for forming the reformed portion, there arevarious methods, for example, such as laser irradiation, electron beamirradiation, local heating using an image furnace, or the like. Amongthese, the laser irradiation is advantageous in a point that theapparatus can be made relatively small, and in a point that anirradiation position of the laser with respect to the ceramic elementbody can be quickly changed. The local heating reforms only a surfacelayer portion of the ceramic element body, and therefore does notsubstantially affect electrical characteristics as an electroniccomponent (e.g., an inductor).

A typical ceramic material which can be reformed by irradiation with thelaser includes ferrite. The ferrite is a ceramic material containingiron oxide as its main component, and examples thereof include spinelferrite, hexagonal ferrite, garnet ferrite, and the like. When theferrite is irradiated with the laser, the irradiated portion is meltedand solidified, and the surface layer portion of the ferrite is changedin quality and has conductivity. Examples of the ferrite used for theinductor include Ni—Zn based ferrite, Mn—Zn based ferrite, Ni—Cu—Znbased ferrite, and the like, and the reformed portion can be formed bythe laser irradiation for any ferrite. A known laser, such as a YAGlaser, a YVO₄ laser, or the like can be used as the laser.

It is preferable that the reformed portion be formed at a position onanother surface of the ceramic element body adjacent to the extendedsurface and close to the extended surface. Even when the base electrodeand the reformed portion are separated from each other, since theplating metal deposited on the base electrode and the reformed portiongrows therebetween at the time of wet plating, the continuous platingelectrode can be formed. When the base electrode and the reformedportion are close to each other or in contact with each other, thecontinuous plating electrode can be formed in a shorter time.

After step (B) in FIG. 12 for forming the base electrode, it ispreferable that step (C) for forming the reformed portion be executed.When the reformed portion is formed before forming the base electrode,there is a possibility that the reformed portion is oxidized by heattreatment when forming the base electrode and is made to be anon-conductor. Therefore, by forming the reformed portion after formingthe base electrode, oxidation of the reformed portion can be suppressed,and a good plating electrode can be formed thereon. Note that when theheat treatment at the base electrode does not affect oxidation of thereformed portion, the reformed portion may be formed earlier than thebase electrode.

As the wet plating method, either method of electrolytic plating andelectroless plating can be used, but the electrolytic plating method iseasy to control a film thickness and is therefore preferable. Since boththe base electrode and the reformed portion formed by the method of thepresent disclosure have conductivity, the plating metal is rapidlydeposited on the base electrode and the reformed portion. In theexisting plating method, when plating is not desired to be applied topart of the ceramic element body, it is necessary for a platingpreventing material to be applied in advance to the portion for coatingor for the plating portion to be removed by cutting or the like. In thepresent disclosure, since the reformed portion can be locally formed ata portion where the base electrode is difficult to be formed, a coatingstep of the plating preventing material or the like can be omitted. Whenthe reformed portion is formed by the laser irradiation, since a surfaceof the reformed portion becomes uneven, there is an advantage in thatthe fixing strength of the plating electrode is enhanced due to ananchor effect.

An another embodiment of the present disclosure provides an electroniccomponent including a ceramic element body made of a ceramic materialcontaining a metal oxide, the ceramic element body having an innerelectrode and having an extended surface to which part of the innerelectrode is extended; a base electrode formed on the extended surfaceof the ceramic element body so as to be connected to the innerelectrode, the base electrode being an electrode formed of a conductivepaste; a reformed portion formed at another surface of the ceramicelement body adjacent to the extended surface and including a reducedmetal element of the metal oxide; and a plating electrode formed on thebase electrode and the reformed portion. The electrode formed of theconductive paste can also be called a metal composite electrodeincluding a metal and glass, or a metal and a resin. Furthermore, theplating electrode can also be called a metal thin film electrode. Inthis case, it is possible to prevent entrance of a plating solution orflux into the extended interface of the inner electrode, and thus it ispossible to obtain the electronic component with improved durability.

One of features of the method of the present disclosure is that anodd-shaped outer electrode can be easily formed. For example, when baseelectrodes are formed on both end surfaces of a rectangularparallelepiped ceramic element body in a longitudinal direction,respectively, and reformed portions (e.g., two portions) are formed onlyat one surface (e.g., a bottom surface) adjacent to both the endsurfaces, a pair of L-shaped outer electrodes can be formed. In otherwords, it is also possible to form the outer electrodes only on both theend surfaces and the bottom surface, and not to form an electrode on anupper surface and both side surfaces in a width direction. Forming theL-shaped outer electrode is advantageous in a point that the parasiticcapacitance between the inner electrode and the outer electrode can bereduced and electrical characteristics of the electronic component canbe improved because the outer electrode is formed only at a portionnecessary for mounting. Additionally, there are an advantage that whenthe electronic component is mounted on a circuit board or the like at ahigh density, an insulating distance from an adjacent electroniccomponent is easily secured, an advantage that when a plurality ofcircuit boards is disposed in parallel to each other in a thicknessdirection, an insulating distance between the electronic component and aconductive portion of the circuit board disposed thereabove is easilysecured, and the like. Furthermore, when the base electrode is formed oneach of the end surfaces with the conductive paste, the reformed portionis formed at the bottom surface, and the plating electrode covering thebase electrode and the reformed portion is formed, since a thickness ofthe outer electrode formed on the bottom surface can be reduced ascompared with a thickness of the outer electrode formed on each of theend surfaces, it is possible to reduce the height of the electroniccomponent.

As described above, according to the present disclosure, since the wetplating is performed after the base electrode is formed on the extendedsurface of the ceramic element body, it is possible to suppress theplating solution from penetrating into the interface between the innerelectrode and the ceramic element body. Additionally, since the reformedportion is formed at the surface of the ceramic element body adjacent tothe extended surface and the plating electrode is formed on the baseelectrode and the reformed portion, it is possible to form the outerelectrode only on the necessary portion. Accordingly, it is possible toeasily form the outer electrode of an arbitrary shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electronic component according to afirst embodiment of the present disclosure;

FIG. 2 is an exploded perspective view of the electronic componentillustrated in FIG. 1 ;

FIG. 3 is a cross-sectional view of the electronic component in FIG. 1when viewed from a Y direction;

FIGS. 4A through 4D include cross-sectional views illustrating steps offorming an outer electrode;

FIG. 5 is a perspective view illustrating an example of a method ofirradiating a ceramic element body with a laser;

FIGS. 6A through 6C include enlarged cross-sectional views of an exampleillustrating a process of forming a reformed portion and a platingelectrode;

FIG. 7 is an enlarged cross-sectional view of an example of a structureof the reformed portion;

FIG. 8 is a graph showing changes in a resistance value of ferritebefore and after the laser irradiation, and changes in the resistancevalue at reheating;

FIGS. 9A through 9C include diagrams illustrating some examples ofstructures of the outer electrode of the ceramic element body in which arounded surface is formed on a corner portion;

FIGS. 10A and 10B include perspective views of some other examples ofthe electronic component according to the present disclosure;

FIGS. 11A through 11D include perspective views illustrating someexamples of two-terminal type electronic components according to thepresent disclosure;

FIG. 12 shows a flowchart illustrating a method of forming the outerelectrode according to the present disclosure; and

FIGS. 13A through 13C include cross-sectional views of an example of anexisting chip component with an outer electrode formed through steps ofa plating method.

DETAILED DESCRIPTION

FIG. 1 illustrates a chip type inductor 1 which is an example of anelectronic component according to the present disclosure. FIG. 1illustrates the inductor 1 such that a bottom surface thereof facesupward. The inductor 1 includes a ceramic element body 10, and outerelectrodes 30 and 31 are formed on both end portions of the ceramicelement body 10 in a length direction, respectively. As illustrated inFIG. 1 , a shape of the inductor 1 of this embodiment is a rectangularparallelepiped shape whose dimension in an X-axis direction is largerthan those in a Y-axis direction and a Z-axis direction. Note that inthis specification, the “rectangular parallelepiped shape” is notlimited to a shape with edge-shaped corner portions, may be a shape withchamfered corner portions or corner portions on each of which a roundedsurface is formed.

As illustrated in FIG. 2 , the ceramic element body 10 is obtained bystacking and sintering insulator layers 12 a to 12 e that take, forexample, Ni—Zn based ferrite, Mn—Zn based ferrite, or Ni—Cu—Zn basedferrite as a primary component. The insulator layers 12 a to 12 e arestacked in this order in a vertical direction (Z-axis direction). On theintermediate insulator layers 12 b to 12 d excluding the insulatorlayers 12 a and 12 e at both upper and lower ends, coil conductors 21 to23 constituting an inner electrode 20 are formed, respectively. Thesethree coil conductors 21 to 23 are connected to each other by viaconductors 24 and 25, and are formed in a spiral shape as a whole. Thecoil conductors 21 to 23 and the via conductors 24 and 25 are formed ofa conductive material such as Au, Ag, Pd, Cu, Ni, and the like. One endportion (extended portion) 21 a of the coil conductor 21 is exposed onone end surface 10 b of the ceramic element body 10 in the X-axisdirection, and one end portion (extended portion) 23 a of the coilconductor 23 is exposed on another end surface 10 a of the ceramicelement body 10 in the X-axis direction. The end surfaces 10 a and 10 bof the ceramic element body 10 where both the end portions 21 a and 23 aof the inner electrode 20 are exposed, respectively, are extendedsurfaces. Note that in this embodiment, an example has been described inwhich the coil conductors 21 to 23 form a coil with two turns, but thenumber of turns is arbitrary, and the shape of the coil conductor andthe number of layers of the insulator layers can also be arbitrarilyselected. Further, the number of layers of the insulator layers 12 a and12 e that do not have the coil conductor is also arbitrary.

As for the outer electrodes 30 and 31, as illustrated in FIG. 3 , whenthe ceramic element body 10 is viewed from the Y direction, the outerelectrodes 30 and 31 are each formed in an L-shape. In other words, theouter electrode 30 is formed in the L-shape so as to cover the one endsurface 10 a in the X-axis direction and part of a bottom surface(mounting surface) 10 c of the ceramic element body 10, and the outerelectrode 31 is formed in the L-shape so as to cover the other endsurface 10 b in the X-axis direction and part of the bottom surface 10 cof the ceramic element body 10. As illustrated in FIG. 3 , the outerelectrode 30 is connected to the extended portion 23 a of the coilconductor 23, and the outer electrode 31 is connected to the extendedportion 21 a of the coil conductor 21. The outer electrodes 30 and 31are each constituted of two kinds of electrodes. In other words, first,a base electrode 301 is formed on each of the end surfaces 10 a and 10 bof the ceramic element body 10, and a plating electrode 302 is formedthereon, so that a double-layer structure is formed. In addition, areformed portion (or low resistance portion) 303 in which the ceramicelement body 10 is changed in quality is formed at each end portion ofthe bottom surface (mounting surface) 10 c of the ceramic element body10, and the plating electrode 302 is also formed on the reformedportion. Note that in FIG. 3 , only the base electrode 301, the platingelectrode 302, and the reformed portion 303 for one end portion of theceramic element body 10 are shown, and the base electrode 301, theplating electrode 302, and the reformed portion 303 for the other endportion are omitted. In FIG. 3 , since the reformed portion 303 isformed in an uneven shape, the surface of the plating electrode 302thereon also has an uneven shape. The plating electrode 302 on the baseelectrode 301 and the plating electrode 302 on the reformed portion 303are formed simultaneously through a wet plating method. For materials ofthe base electrode 301 and the plating electrode 302, for example, Cu,Au, Ag, Pd, Ni, Sn or the like is used, and both electrodes may be madeof the same metal material or different metal materials. Note that theplating electrode 302 is not limited to have one layer, and may beconstituted of multiple plating layers. It is preferable that theplating electrode of the outermost layer be made of a material havinggood solder wettability.

The method of forming the base electrode 301 is the same as a knownmethod using a conductive paste. In other words, a method of dipping theend portion of the ceramic element body 10 into a conductive paste filmformed with a predetermined thickness, a method of using a transfer bysuch as a roller, and the like are available. It is to be noted that bysetting the film thickness of the conductive paste and the dipping depthof the ceramic element body 10, it is possible to adjust whether theconductive paste is applied only to the end surface of the ceramicelement body 10 or applied so as to wrap around the surface adjacent tothe end surface. Furthermore, it is not necessary for the applicationregion of the conductive paste to be the entire surfaces of the endsurfaces 10 a and 10 b of the ceramic element body 10, and it issufficient that the conductive paste is applied to at least a portionwhere the extended portions 23 a and 21 a of the inner electrode 20 areexposed. After applying the conductive paste, the ceramic element bodyis subjected to heat treatment at a predetermined temperature to formthe base electrode 301. There are two methods for the heat treatment,and when a baking type conductive paste is used, the heat treatment isperformed until glass and metal powder contained in the conductive pasteare sintered. When a thermosetting type conductive paste is used, athermosetting resin contained in the conductive paste is cured by theheat treatment. The baking type conductive paste has a higher heattreatment temperature than that of the thermosetting type conductivepaste.

In this way, when the base electrodes 301 are formed using theconductive paste, the base electrodes 301 are formed on the end surfaces10 a and 10 b of the ceramic element body 10 on which the extendedportions 23 a and 21 a of the inner electrode 20 are exposed,respectively, and are electrically connected to the extended portions 23a and 21 a, respectively, as shown in FIG. 4A. As illustrated in FIG.4B, when the ceramic element body 10 is fired, a gap 5 may be generatedin the end surface of the ceramic element body 10 to which the innerelectrode 20 is extended due to a difference in shrinkage between theceramic element body 10 and the inner electrode 20 in some cases.However, as illustrated in FIG. 4C, when the conductive paste isapplied, a conductive paste 301 a can close the gap S. Accordingly, itis possible to prevent a plating solution from entering the gap 5 in thewet plating performed thereafter as illustrated in FIG. 4D. The platingelectrode 302 is formed on the base electrode 301.

FIG. 5 illustrates a method of forming the reformed portions 303 using alaser L at both end portions (electrode forming regions S1) of thebottom surface 10 c of the ceramic element body 10 in the lengthdirection. Here, an example is illustrated in which the ceramic elementbody 10 after the base electrode 301 is formed is irradiated with thelaser L, but the ceramic element body 10 before the base electrode 301is formed may be irradiated with the laser L. There is a plurality ofirradiation methods of the laser L, and in this case, an example ofscanning along the Y-axis direction while performing continuousirradiation by the laser L (or an example in which the ceramic elementbody 10 is moved in the Y-axis direction) is illustrated. The scanningby the laser is performed in an arbitrary direction, may be performed inthe X-axis direction, or may be performed in a zigzag shape, or acircular shape. By the irradiation of the laser L, a large number oflinear laser irradiation marks 304 are formed on the surface of theceramic element body 10, and the reformed portion 303 is formed at abottom portion of the irradiation marks 304. Note that FIG. 5illustrates an example in which the linear laser irradiation marks 304are formed with intervals in the X-axis direction, but the laserirradiation marks 304 may be densely formed so as to overlap with eachother. In addition, instead of the method of continuous irradiation ofthe laser L, intermittent irradiation may be performed. In any case, itis desirable to uniformly irradiate the entire region of the electrodeforming regions S1 and S2 with the laser L.

FIGS. 6A through 6C illustrate an example of a process of forming thereformed portion 303 and the plating electrode 302. FIG. 6A illustratesa state in which the bottom surface 10 c of the ceramic element body 10which is close to the base electrode 301 is irradiated with the laser L,thereby forming the laser irradiation mark 304 having a V-shaped orU-shaped cross section on the surface of the ceramic element body 10.Note that although FIG. 6A illustrates an example in which the laser Lconverges at one point, in practice, a spot irradiated with the laser Lmay have a certain area. This laser irradiation mark 304 is a mark inwhich a surface layer portion of the ceramic element body 10 is meltedand solidified by the laser irradiation. Since the central portion ofthe spot has the highest energy, the ceramic material of the portion iseasily changed in quality, and thus the cross section of the laserirradiation mark 304 is substantially V-shaped or substantiallyU-shaped. A metal oxide (in this case, ferrite) constituting the ceramicelement body is changed in quality/reduced, and the reformed portion 303having a lower resistance value than that of the metal oxide is formed,in the periphery including an inner wall surface of the laserirradiation mark 304. As one of factors for lowering the resistancevalue of the ferrite material, a reduction reaction is cited in whichFe₂O₃ contained in the ferrite changes into Fe3O4 having a lowerresistance value. In addition, in the case of Ni—Zn based ferrite, thereis a possibility that part of Fe containing material is reduced and partof Ni and/or Zn containing material is also reduced. In the case ofNi—Cu—Zn based ferrite, there is a possibility that Fe and/or Cu isreduced and Ni and/or Zn is also reduced. A depth and an area of thereformed portion 303 can be varied depending on irradiation energy, anirradiation range, and the like of the laser.

FIG. 6B illustrates a case where irradiation of the laser L with aninterval D in the x direction is performed and the electrode formingregion S1 is densely irradiated such that the plurality of laserirradiation marks 304 is densely formed. The expression “denselyirradiated” means that the interval D between spot centers of the laserirradiation is equal to or smaller than an expansion width (e.g., anaverage value of a diameter) W of the reformed portion 303, andindicates a state in which the reformed portions 303 formed on a lowerside of the laser irradiation marks 304 adjacent to each other areconnected to each other. However, it is not necessary for all of thereformed portions 303 to be connected to each other. Therefore,substantially the entire region of the electrode forming region S1 ofthe ceramic element body 10 is covered with the reformed portions 303.

FIG. 6C illustrates a state in which a plating process is performed onthe ceramic element body 10 on which the base electrode 301 and thereformed portion have been formed as described above. Since a currentdensity of the conductive base electrode 301 and reformed portion 303becomes higher than those of the other portions, the plating metal isquickly deposited on the surfaces of the base electrode 301 and thereformed portion 303, and then the continuous plating electrode 302 isformed thereacross. In other words, the plating metal deposited on thebase electrode 301 and the reformed portion 303 becomes a core and growsto the periphery, and even if an insulating region is present betweenthe base electrode 301 and the reformed portion 303, the continuousplating electrode 302 is formed in a short period of time. In this way,the L-shaped outer electrode 30 is formed.

By controlling the plating process time and a voltage or a current, itis possible to control the formation time and the thickness of theplating electrode. Furthermore, by performing an additional platingprocess on the plating electrode 302 formed by the first platingprocess, it is also possible to form a plating electrode having amultilayer structure. In this case, since the plating electrode servingas a base is already formed, an additional plating process time can beshortened.

Although FIGS. 6A through 6C illustrate an example in which the denselaser irradiation (D≤W) is performed, it is also possible to performirradiation with the interval D wider than the expansion width W of thereformed portion 303 (D>W). In this case, although the insulating regionother than the reformed portion, that is, a region in which the originalmetal oxide constituting the ceramic element body is not changed inquality is exposed between the laser irradiation marks 304, in theplating process step which is performed later, the continuous platingelectrode can also be formed on the insulating region with ease becausethe plating electrode grows between the reformed portions 303.

FIG. 7 illustrates an example of a cross-sectional structure of thereformed portion 303 which is formed in this manner. A reduction layer303 a is formed in a lower layer, and a surface layer thereof is coveredwith a reoxidation layer 303 b made of a component of a semiconductorand/or an insulator. The reduction layer and the reoxidation layerconstitute the reformed portion 303. Note that the laser irradiation isnot limited to be performed in the air atmosphere, the laser irradiationmay be performed in a vacuum or an N₂ atmosphere, but when the laserirradiation is performed in the vacuum or the N₂ atmosphere, there is apossibility that the reoxidation layer is not formed.

When the above-described reoxidation layer is formed, the followingeffects can be condsidered. In other words, Fe₃O₄ formed as thereoxidation layer has the property of hardly causing the reoxidation ata normal temperature, suppresses the oxidation of the reduction layer ofthe lower layer, and also has an effect capable of suppressing change inthe reoxidation layer itself with time. Furthermore, the reoxidationlayer is a kind of a semiconductor, and has a lower resistance valuethan that of ferrite being the insulator, and has a smaller thickness.Therefore, even if the reoxidation layer is formed, the depositionproperty of the plating metal is not affected.

In the above description, the reformed portion is formed after formingthe base electrode, but it is also possible to reverse the formationorder thereof. In other words, it is also possible to form the baseelectrode after forming the reformed portion. However, when the bakingtype conductive paste is used as the base electrode, it is desirable toform the reformed portion after the base electrode is formed. This isbecause, when the reformed portion is formed before forming the baseelectrode, there is a possibility that the reformed portion is oxidizedby heat treatment at the time of forming the base electrode and is madeto be a non-conductor. Being made to be a non-conductor may inhibitdeposition of the plating electrodes during the plating process whichwill be performed later. Therefore, when the baking type conductivepaste is used, the oxidation of the reformed portion can be suppressedby forming the reformed portion after forming the base electrode.

FIG. 8 shows a relationship between the conductivity of the reformedportion and the heat treatment temperature. That is, for the ferritematerial as a target, results of measuring change in the resistancevalue of the ferrite before the irradiation and after the irradiation ofthe laser, and the resistance value when the temperature is raised againafter forming the reformed portion are shown. In FIG. 8 , a surfaceresistance is obtained by causing a probe to make contact with a surfaceof the material with regular intervals, and measuring the resistancevalue therebetween. As is apparent from FIG. 8 , whichever laser amongthe three kinds of lasers is used for the irradiation, the resistancevalue of the ferrite material is reduced by amount of approximately10⁻⁸, and thus it can be seen that the reformed portion is certainlyformed. On the other hand, when the temperature is raised to 300° C.,the resistance value of the reformed portion hardly increases, but byraising the temperature to equal to or higher than 600° C. again, thereformed portion takes behavior of the reoxidation, and the tendency ofthe resistance value to increase significantly can be confirmed. Ingeneral, when the thermosetting type conductive paste is used as thebase electrode, since a thermosetting temperature is approximately 200°C., the resistance value of the reformed portion is considered to hardlyincrease, but the heat treatment temperature of the baking type is equalto or higher than 600° C. in some cases, and therefore the reoxidationof the reformed portion cannot be suppressed. As described above, when aflow of forming the base electrode after forming the reformed portion isperformed, when the baking temperature and the curing temperature of thebase electrode are at a certain level (e.g., 600° C.) or higher, theresistance value of the reformed portion increases, and there is apossibility that the deposition of the plating is not achieved in thesubsequent plating step. Accordingly, it is desirable to employ the flowof forming the reformed portion after forming the base electrode. Notethat when this process in which the temperature is raised again isperformed in the N₂ atmosphere, the reoxidation reaction is suppressedas compared with the case where the process is performed in the air, andtherefore the increase amount of the resistance value is suppressed.

—Experimental Example—

Hereinafter, an experimental example in which the reformed portion andthe plating electrode are formed will be described.

(1) A sintered ceramic element body made of Ni—Cu—Zn based ferrite wasirradiated with a laser with a reciprocating scan. The processingconditions are as follows, but a wavelength may be, for example, in anyrange of 532 nm to 10620 nm. An irradiation interval means a distancebetween the spot centers of a forward path and a backward path in thecase of the reciprocating scan by the laser.

TABLE 1 [Laser Processing Condition] Wavelength 1064 nm (YVO4) Output 14A Scanning Speed 200 mm/s Q switch Frequency 20 kHz Irradiation Interval(pitch) 30 μm Spot Diameter 70 μm Energy Density 1 J/sec

(2) Electrolytic plating was carried out on the ceramic element bodyafter the laser irradiation under the following conditions.Specifically, barrel plating was used.

TABLE 2 [Plating Condition] Plating Solution Copper pyrophosphateplating solution Rotation Speed [rpm] 24 rpm Current [A] 12 ATemperature [° C.] 55° C. Time 8 min

As a result of performing the plating process under the aboveconditions, forming a good Cu outer electrode having an averagethickness of approximately 2 μm on the surface of the ceramic elementbody was performed. Note that similar results were obtained even whenNi—Zn based ferrite was used. Furthermore, as the plating solution, acopper sulfate plating solution, a copper cyanide plating solution, orthe like can also be used in addition to the copper pyrophosphateplating solution.

—Evaluation—

For a sample irradiated with the laser and a sample not irradiated withthe laser of the Ni—Cu—Zn based ferrite, the valence of Fe, Cu and Zn onthe surfaces of the samples were evaluated, by a K-end XAFS (X-rayabsorption fine structure) of Fe, Cu, and Zn using an XPS (X-rayphotoelectron spectroscopy) and a conversion electron yield method. As aresult of the XPS, a metal component could not be detected at thesurface layer portion of the sample irradiated with the laser, and ametal component could be detected at the lower layer portion.Additionally, as a result of the XAFS, the metal component of Cu couldbe detected at the surface layer portion of the sample irradiated withthe laser. On the other hand, as the result of the XAFS, although themetal component of Fe could not be detected at the surface layer portionof the sample irradiated with the laser, the semiconductor component ofFe and the insulator component could be detected. It was also found thata ratio of Fe²⁺ to Fe³⁺ in the lower layer is larger than the ratio inthe entire ceramic element body. Accordingly, it is estimated that themetal oxide contained in the ferrite is decomposed by the heat generatedby the laser processing, the lower layer of the ceramic element body isreduced to the metal element of the ferrite, and the surface layerportion of the ceramic element body is reoxidized by residual heat.

In the case of the electronic component 1 with the L-shaped outerelectrodes 30 and 31 being formed as illustrated in FIG. 1 , thefollowing differences also occur in addition to the differences in theelectrical characteristics as described above. In other words, since theouter electrode is not formed on the upper surface of the electroniccomponent 1, it is possible to reduce a risk of occurrence of a shortcircuit even when another electronic component or a conductor is closelypresent above the electronic component 1 in a mounting state.Furthermore, since the outer electrode is not also formed on both sidesurfaces in the Y direction, even when another electronic component 3 ismounted adjacent to the electronic component 1 in the Y direction, it ispossible to secure an insulating distance from the adjacent electroniccomponent and to secure a distance of the solder applied to the outerelectrodes. Therefore, it is possible to reduce the risk of the shortcircuit with the adjacent electronic component. As a result, in the caseof the electronic component 1 with the L-shaped outer electrode, afurther high-density mounting can be achieved.

FIGS. 9A through 9C illustrate an example of a structure of the L-shapedouter electrode formed using the present disclosure. In FIG. 9A, whenrounded surfaces R1 and R2 are formed at corner portions of the ceramicelement body 10, an edge portion of the base electrode 301 is formed soas to extend to the rounded surfaces R1 and R2, and the reformed portion303 is formed at each of the end portions of the bottom surface 10 c ofthe ceramic element body 10 so as to be in contact with the baseelectrode 301. The plating electrode 302 is continuously formed on thebase electrode 301 and the reformed portion 303, and the L-shaped outerelectrodes 30 and 31 are each formed. As described above, when therounded surface is formed at a boundary portion between each of the endsurfaces 10 a and 10 b and another surface adjacent thereto (includingthe bottom surface 10 c), since part of the base electrode 301 can becaused to wrap around the other surface while maintaining apredetermined film thickness when the base electrode 301 is formed oneach of the end surfaces 10 a and 10 b, the reformed portion 303 can beeasily formed in a contact/proximity state with the base electrode 301.

In FIG. 9B, the upper surface side edge portion of the base electrode301 is formed so as not to extend to the rounded surface R1 of theceramic element body 10, and the bottom surface side edge portion isformed so as to extend to the rounded surface R2 of the ceramic elementbody 10. In this case as well, the reformed portion 303 can be formed atthe bottom surface 10 c of the ceramic element body 10 so as to be incontact with the base electrode 301.

In FIG. 9C, the base electrode 301 is formed only on each of the endsurfaces 10 a and 10 b of the ceramic element body 10. In other words,the edge portions of the base electrode 301 are formed so as not toextend to the rounded surfaces R1 and R2 of the ceramic element body 10,respectively. The reformed portion 303 is formed so as to extend to therounded surface R2 on the bottom surface side of the ceramic elementbody 10, that is, so as to be in contact with the base electrode 301. Asa result, the plating electrode 302 is continuously formed on the baseelectrode 301 and the reformed portion 303.

FIG. 10 illustrates another example of the electronic component with theouter electrode formed using the present disclosure. FIG. 10Aillustrates an electronic component with the outer electrodes 30 and 31formed on both the end portions of the bottom surface 10 c in the xdirection and both the end surfaces 10 a and 10 b in the x direction ofthe ceramic element body 10 (illustrated upside down in FIGS. 10A and10B), respectively. No outer electrode is formed on the other surfaces.In this case, the end portions 21 a and 23 a of the inner electrode arenot exposed on both the end surfaces 10 a and 10 b of the ceramicelement body 10, and are exposed only on the bottom surface 10 c. On thebottom surface 10 c of the ceramic element body 10, the base electrode301 is formed so as to be connected to each of the end portions 23 a and21 a of the inner electrode. The reformed portion 303 is formed at eachof the end surfaces 10 a and 10 b of the ceramic element body 10, theplating electrode (not illustrated) is continuously formed on the baseelectrode 301 and the reformed portion 303, and each of the outerelectrodes 30 and 31 is formed. In this embodiment, the reformed portion303 is formed only on the bottom surface side of each of the endsurfaces 10 a and 10 b, but the reformed portion 303 may be formed overthe entire surface of each of the end surfaces 10 a and 10 b.

FIG. 10B illustrates a multi-terminal type electronic component. In thisexample, the extended portions 21 a and 23 a of the inner electrode arenot exposed on both the end surfaces 10 a and 10 b of the ceramicelement body 10, and exposed on both side surfaces 10 d and 10 e in they direction. The base electrode 301 is formed on each of the sidesurfaces 10 d and 10 e, and the base electrode 301 and each of theextended portions 21 a and 23 a of the inner electrode are connected toeach other. The reformed portions 303 are formed at four portions on thebottom surface 10 c (the surface on the upper side in FIG. 10B) of theceramic element body 10, respectively. The plating electrode (notillustrated) is continuously formed on the base electrode 301 and thereformed portion 303, and each of the four outer electrodes 30 to 33 isformed. No outer electrode is formed on both the end surfaces 10 a and10 b in the x direction and the upper surface (the surface on the lowerside in FIGS. 10A and 10B).

FIGS. 11A through 11D illustrate another example in which the presentdisclosure is applied to a two-terminal type chip component. In FIG.11A, the base electrode 301 is formed on each of the end surfaces of theceramic element body 10, and the two reformed portions 303 are formed ateach of the end portions of the bottom surface 10 c. Note that theplating electrode formed on the base electrode 301 and the reformedportion 303 is omitted. In this case, since the electrode on the bottomsurface side is divided into two portions, there is an advantage in thatthe mounting stability is improved at the time of soldering to thecircuit board.

FIG. 11B is the same as FIG. 11A in a point that the reformed portion303 formed at the bottom surface is divided into two portions, but isdifferent in a point that the base electrode 301 formed on each of theend surfaces is formed only on part of the bottom portion side.

In FIG. 11C, the base electrode 301 is formed not on the entire surfaceof each of the end surfaces 10 a and 10 b but in a narrow band shapeextending in the vertical direction only at the central portion. Thereformed portion 303 on the bottom surface 10 c side is formed in a bandshape continuous in the width direction.

FIG. 11D is the same as FIG. 1 in a point that the base electrode 301 isformed on each of the end surfaces 10 a and 10 b and the reformedportion 303 is formed on each end side of the bottom surface 10 c, butis different in a point that part of the reformed portion 303 extends toboth the front and rear side surfaces 10 d and 10 e.

In the above-described embodiment, an example in which the presentdisclosure is applied to formation of the outer electrode of the chiptype inductor has been described, but the present disclosure is notlimited thereto. An electronic component to which the present disclosureis applied is not limited to the inductor, the present disclosure can beapplied to an electronic component which uses the ceramic element bodyin which the quality is changed by the laser irradiation and thereformed portion serving as the deposition starting point of the platingelectrode is formed. In other words, the material of the ceramic elementbody is not limited to ferrite. Although an example using electrolyticplating has been described as the wet plating method, the electrolessplating may be used.

In the embodiment described above, the laser irradiation is used as thelocal heating method, but electron beam irradiation, heating using animage furnace, or the like is also applicable. In any case, since theenergy of the heat source can be collected and the ceramic element bodycan be locally heated, the electrical characteristics of the otherregions can be prevented from being damaged.

In the present disclosure, when the laser is used for the local heating,one laser may be split and a plurality of portions may be simultaneouslyirradiated with the split lasers. Furthermore, a laser focus may beshifted to widen an irradiation range of the laser as compared with acase where the laser is focused.

The present disclosure is not limited to a case where, when the platingmetal includes a plurality of layers, the lowermost layer of the platingmetal is grown so as to spread over the entire region of the baseelectrode and the reformed portion. The lowermost layer of the platingmetal may be grown so as to spread to part of the base electrode and thereformed portion, and an upper layer of the plating metal may be grownso as to spread over the entire region of the base electrode and thereformed portion.

What is claimed is:
 1. An electronic component comprising: a ceramicelement body including a ceramic material containing a metal oxide, theceramic element body having an inner electrode and having an extendedsurface to which part of the inner electrode is extended; a baseelectrode on the extended surface of the ceramic element body andconnected to the inner electrode, the base electrode being an electrodeconfigured by a conductive paste; a reformed portion at another surfaceof the ceramic element body adjacent to the extended surface andincluding a reduced metal element of the metal oxide; and a platingelectrode on the base electrode and the reformed portion.
 2. Theelectronic component according to claim 1, wherein the ceramic elementbody has a rectangular parallelepiped shape, the extended surface iseach end surface of the ceramic element body in a longitudinaldirection, the surface at which the reformed portion is present is abottom surface of the ceramic element body, and the reformed portion ispresent at each end portion of the bottom surface in the longitudinaldirection.